Gabriel Munar-Delgado, Marion Nicolaus, Christiaan Both, Pim Edelaar

Evolutionary ecology has traditionally studied how natural selection shapes the phenotypes of individuals in response to their environment, which increases population fitness. It is also well known how habitat choice can affect individual local adaptation. However, recent work has highlighted the incompleteness of the link between habitat choice and its evolutionary consequences. By treating the selected habitat as an extended phenotype, the evolutionary focus can be shifted to how the extended phenotype evolves to match the organisms' phenotypic traits. Theoretical approximations suggest that animal models could be used to estimate the heritability of the extended phenotype, providing insights into its evolutionary dynamics. Here we use data from a long-term study of a pied flycatcher population (Ficedula hypoleuca) to test the use of animal models for the estimation of the heritability of an extended phenotype i: the vegetation around the nest box. We also applied animal models to different subsets of the population (based on philopatric status) to test which mechanism might be causing the inheritance of the extended phenotype, if any. We also ran simulations to randomize the nest box and its surrounding vegetation for the different population subsets, thereby eliminating the effect of habitat choice, and used the animal models to identify the sources of variation of the extended phenotype. We confirmed that animal models can be used to estimate the local habitat heritability in natural populations and found a significant habitat heritability for our pied flycatcher population. Moreover, subset analysis and subset randomization both
indicated that the observed heritability was caused by philopatry. Thus, we propose that animal models can be used to estimate the heritability of the extended phenotype and also to disentangle the mechanism(s) causing its inheritance. By acknowledging that organisms can influence the habitat they experience to increase their adaptation and by focusing on the evolution of extended phenotype, we should be able to better understand how population adaptation increases and how it evolves.